1. Field of the Invention
This invention relates generally to filters for smoking articles and more particularly to filtering devices for controlling the amount of smoke drawn through a smoking article such as cigarettes, cigars and the like.
2. Description of the Prior Art
Various types of filters have been designed for removing or reducing undesirable constituents in the smoke from smoking articles. Most commonly, such filters take the form of a mass of fibers, paper or other porous and semiporous materials through which the smoke must pass, thereby entraining some of the constituents present in the smoke.
Other types of smoke filterng devices have been proposed which utilize valves or various designs which tend to open upon a predetermined amount of suction being applied by the smoker when drawing on the smoking article. Typical devices of this nature are disclosed in U.S. Pat. Nos. 2,709,441; 3,533,414; 3,616,802; and 3,685,522. However, filter valves of this type have the disadvantage of increasing the amount of smoke drawn through the smoking article as the pressure or suction is increased by the draw in any individual puff, thereby opening the valve and thus increasing the amount of smoke and attendant constituents passing through the valve to the smoker.
Cigarette filter devices have also been proposed that contain valves which are designed to close by the hot smoke from the approaching coal as the cigarette is smoked and thereby reduce the amount of smoke that can be drawn through the cigarette, particularly in the last half of the cigarette. Examples of this type of filter valve are disclosed in U.S. Pat. No. 3,800,805. However, such valves have the disadvantage that they are responsive to the heat from the smoke and only operate to close when the heat gets high enough or the burning coal close enough to activate the valve. At all other times the valve remains open without any restriction placed upon the amount of smoke that can be drawn through the cigarette.
All of the foregoing disadvantages become important when considered in light of the new lower tar and nicotine cigarettes currently being produced. Many smokers in order to achieve the same level of nicotine they have been accustomed to tend to draw harder with a greater volume of smoke in each puff, thereby obtaining a greater yield of nicotine and tar in each puff and defeating the purpose for which the such cigarettes were designed.
Accordingly, it is an object of this invention to provide a smoke control device for smoking articles and the like not having the disadvantages of the above prior art filter devices. Another object of this invention is to provide a smoke control device which will limit the volume of smoke that can be drawn in any puff depending upon the pressure drop or rate of draw induced by the smoker.